Crystallization behavior of poly(ε-caprolactone) and poly (ε-caprolactone)/LiClO ₄ complexes from the melt

The crystalline structures and isothermal crystallization behavior of poly(ε-caprolactone) (PCL) and PCL/LiClO ₄ complexes from the melt were investigated via time-resolved simultaneous synchrotron small-angle and wide-angle X-ray scattering (SAXS/WAXS) measurements in this paper. The influences of Li salts and crystallization temperature on the isothermal crystallization behavior and structural evolution dynamics of PCL were discussed. The results indicated that Li salts affected the crystallization behavior of PCL without changing the structure of the crystalline. It was also shown that the formation of pre-ordered phase (according to SAXS) in the induction stage prior to the appearance of crystalline peaks (according to WAXS) during the isothermal crystallization of PCL and PCL/LiClO ₄ complexes. The collected SAXS data were analyzed according to Guinier plot and correlation function. By comparing the average radius size of isolated domains formed in the melt obtained from the Guinier plot in the early stage of crystallization with the crystalline lamellar thickness calculated according to the correlation function in the later stage of crystallization, it is concluded that the final crystalline structure may evolve from pre-ordered phase in the initial stage of the melt. Through accurate analysis the PCL and PCL/LiClO ₄ complexes depicted invariant SAXS intensities, it is found that the LiClO ₄ coordinated PCL chains mainly locate at the interphase between the crystalline lamellae and amorphous layer. The structural evolution during crystallization in the induction period and subsequent stages of PCL and PCL/LiClO ₄ were analyzed according to a proposed model.